text:
Why is there a radioactivity sign on the Eurofighter's missile?
In this link you see a Eurofighter Typhoon having a missile with a radioactivity sign on it. The inscription below "DANGER" is too small, I can't read it. This is an Austrian Eurofighter plane, so it can't be a nuke, can it?
Edit: I just figured out you can zoom in to read it. Sorry for asking.

"Danger - Radio frequency decoy dispenser"
So not radioactive, but rather radio wavelength emissions.
Quite possibly similar to this:
https://www.baesystems.com/en/product/anale55-fiberoptic-towed-decoy
"AN/ALE-55 fiber-optic towed decoy"

Do you know why they are using the symbol for ionizing radiation, rather than this one for non-ionizing radiation warning?

@Bianfable: I've got two guesses: a) they don't know any better, b) they do know better, but are not sure everybody else does.

@JörgWMittag That's what I thought too, many people probably know the ionizing sign but not the other one.

The link is dead.

My link? Works just fine for me.


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What would have happened if the space balloonists had opened their parachute immediately when jumping off?
What would have happened if Joe Kittinger, Felix Baumgartner and Alan Eustace had opened their parachute right after jumping off the capsule (respectively releasing oneself from the balloon in case of Eustace)? At first it probably wouldn't matter as the chutes would be needless in the near-vacuum the balloonists jumped from, but how exactly would an open parachute have altered their falls? And would something happen to the parachute itself?

You might take a try at calculating parachute "Max Q" based the drag coefficient of an open hemisphere, velocity (from Baumgartner), and atmospheric density at various altitudes.  Because the 'chute is always open, all terminal velocities will be less, the key will be if one slows down at a greater or less rate than  density increases.  Transonic effects would be interesting, but would occur where air is less dense.  Find out where Baumgartner went subsonic.

If it were the Loony Tunes world, the jumper would float at the same height as the platform until they pulled out some old-school bellows to inflate the parachute.  Only then would they start to fall.

All these 3 were high-altitude balloons, not space ones.

If it took any longer they might have had to amputate his hand.

@QuoraFeans The Space Shuttle wasn't a space shuttle either, it was a high-altitude shuttle. The Earth's atmosphere extends until 6,200 or more miles from the surface, hence the only literal spacecraft was the Apollo, the only crewed vehicle having gone beyond 6,200 miles so far.

@RobertDiGiovanni The following graph might be of interest: https://commons.wikimedia.org/wiki/File:Stratos_descent_graph.svg

It is a Loony Tunes world, but that doesn't stop good science.  If we're worried about the parachute opening, take a good strong delta glider up next time.

@Betternottell: Some define the boundary of  space (the Kármán line) as beginning 100 kilometres above Earth's  sea level. The space shuttle went to space according to this definition (but it was not a shuttle, since a shuttle operates at frequent intervals non-stop between two places). For advertisement purposes, of course, Baumgartner claimed it was a space jump.

@QuoraFeans Except that the Kármán line itself varies depending on the body in question and other factors. https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line#Technical_considerations The values usually given are well below that beautiful round metric number. Others would consider the boundary at the stratopause (which is also the bottom of the ionospheric D-layer), the mesopause (which is the same altitude as the turbopause), the triple point of water pressure (at 35 km / 22 mi) or the Armstrong line (at 19 km / 12 mi). You see it's a matter of definition.

The one who made the edit, thanks for the grammar correction.

tl;dr Opening too high will kill you.
As you note, the parachute would just hang next to them immediately after leaving the balloon -- there's too little air that high to even drag the shroud lines out straight.
Later on, there would come a point when the canopy would fill, probably while the jumper was near Mach 1: the air would become thick enough to drag the parachute out to the end of the shrouds and pressure inside the canopy would build enough to shape the parachute.  Assuming it doesn't tangle and fail in one of several ways (this is a real hazard if the lines are slack at any point), there's still the danger of the canopy opening abruptly.  Even in the thin air above 40 km (25 mi), a canopy sized for a man in a pressure suit is capable of generating an opening shock -- the G force from the sudden deceleration as the canopy shapes and its drag force becomes measurable in tons -- sufficient to deal severe injury.  Historically, this has caused broken necks and backs even with parachutes opening at a mere 100-150 m/s (330-490 ft/s) in denser air.
This is why it's normal even with a bail-out at jet altitude to free fall to within a couple kilometers of ground level -- because the lower you get, the slower you fall.  Rising air density reduces your terminal velocity from, in the case of Baumgartner, at least, near Mach 1 to only 50-60 m/s (160-200 ft/s).
Of course, with opening shock that high, there's also the possibility (nay, likelihood) that some part of the parachute system will fail under loads tens of times what they were designed to take.  Shroud lines can snap, canopy fabric rip, etc.  This can lead to an open parachute that doesn't provide the low fall speed it should, or a streamer -- potentially with a badly injured jumper who isn't functional enough to cut away and open his reserve.
Bottom line, these men had a very carefully thought out system to get them down safely: their drogue to stabilize their fall when there was barely enough air to make a self-inflating drogue pull its line straight, and their long, long fall under drogue before opening their main low enough that the opening shock wouldn't break anything.
From comments, there's a question whether there's a midway opening altitude where the parachute can fill, but the air is too thin to produce injurious opening force.  I don't know that this has been studied in detail, but there are altitudes within the envelope of various aircraft (high altitude interceptors and the SR-71 they were designed to try to intercept) at which it might be possible to open safely -- perhaps between about 18 and 20 or so kilometers (59-65,000 ft) -- but doing so would be a bad idea for another reason: there's a limited supply of breathing oxygen in the "bail-out bottle" attached to a pilot's pressure suit, and a parachute descent from above some altitude (guessing, but it's probably lower than 15 km (49,000 ft)) will result in depletion of this oxygen reserve and hypoxia well before descending into air thick enough to breathe directly.

Thank you. I should clarify that Eustace used a drogue for his entire fall, not Baumgartner.

Much as I enjoy the green checkmark, it's usually recommended to allow 24 hours or more -- an accepted answer tends to discourage other answers, and you might prevent a better answer than mine from being written.

I don't know what should be added as you answered basically all I wanted to learn, and then there are people who complain why you don't accept an answer. I reject accepting anyway, especially since accepted answers aren't being pinned, upvotes should suffice (but unregistered users can't upvote).

What would happen without a drogue? Wouldn't the jumper eventually slow to low altitude terminal velocity? Or is it their suit would heat up too much from air fiction while slowing from insane Mach 1 to sane speed would be too high? If so, are we sure it would heat up too much?

@Bohemian It's a fail-safe. Stable freefall needs you to hold a particular body position. If you're a mass suspended under a drogue, you can pass out and still come down stably.

@Graham stably, but too fast to survive impact, so not especially useful. Even in diving posture, terminal velocity only goes up from 120mph to 180mph. If you were willing to waive passing out, could the drogue be omitted with a low altitude, belly down, standard opening given that one would slow pretty quickly once the air became thick below say 5000ft

@Bohemian Sure, you wouldn't survive impact, but it's a long way down. :) If you pass out through instability when you're high, you've got some time to wake up before you impact.

The other function of the drogue is to reduce the tendency to spin.  This is well documented in multiple high altitude fighter bail-outs; it's almost impossible to prevent spinning one direction or the other at rates that can induce loss of consciousness.  IIRC Baumgartner had this as well.  And if you pass out due to spin, you might well die (G/pressure induced stroke etc.) before you get low enough to control the spin.

This is an argument against pulling immediately after jumping, but it seems to me there must be a position between chute-won't-deploy and chute-deploys-catastrophically.  The opening force will go up as the jumper descends into thicker air, it won't be discontinuous.  Thus there should be a fairly high altitude point where it's safe to open.

@LorenPechtel There is not, not from this kind of altitude.  By the time you have enough air to fill the parachute, you're falling so fast that even in thin air the opening shock is almost certain to do you serious injury.  Opening force goes up as velocity increases, more so than as the air thickens.  Even from, say, 20 km (within the envelope of a number of interceptors), however, if you open immediately you'll run out of oxygen in your bail-out bottle well before you get into air thick enough to open your helmet.

@LorenPechtel A specially designed parachute might permit this -- NASA has parachutes that can open at supersonic speeds without destroying themselves or their payload, using reefing lines and staged opening in a heavily vented canopy, but this is a large drogue, not the parachute that will give final descent velocity.  Carrying this kind of drogue and its reserve, plus your main and reserve, would become an impractical load just for exiting the balloon capsule.

I'm wondering if the chute would really experience shock loads at any stage during fall if it was opened immediately after exiting the capsule? The speed and air density would build up gradually, there is no abrupt change in air density (or any other physical property) in the atmosphere. Is there some sort of a "coffin corner" effect here (sorry for obscure term)?

@Jpe61 The issue is that at the point the air gets thick enough to fill the canopy, the jumper is likely still superonic, so the opening will be catastrophic -- it'll go from not enough pressure differential to open the canopy to full open at Mach 1+ in a second or less -- and that's a force increase roundly a thousand-fold, from an unopened wad of parachute material to a fully open canopy.  Delay panels as used on modern flat canopies aren't designed to deal with this, and such don't generally exist on a round parachute.

This is kinda what I was thinking with my reference to coffin corner. It would be sorta same kind of situation as with a plane, say, U-2 flying the maximum and minimum speed at the same time, any change either way would be catastrophic. High altitude aerodynamics are weird...

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Why do budget airlines not use the jetbridge that's right there?
Related to Who decides whether an airline docks at a jetbridge or parks at a remote stand?, but I'm not asking about remote stands.
I recently took an easyJet flight (A319/320) from London Gatwick (LGW) to Malaga (AGP), and once through the gate, we walked down some stairs adjacent to the jetbridge and out to the plane. We didn't use a bus.
But the airbridge was right there. Why not use it?

Maybe the jet bridge wasn't operational? Was this a common theme with all the other gates, or just that one?

Hmmm. Good question. Unknown. This has happened sufficiently often (in my experience) with budget airlines that they can't all be inop jet bridges.

There may be additional fees for using the jet bridges at the airport as well, so they may only use them in bad weather. Hopefully somebody knows the answer but airports charge fees for everything, it may be a tactic to avoid a fee.

This answer to a similar question is real fun to read (especially the last paragraph) and proposes that fees are the definitive reason.

The answer to the question you link explain many of the reasons. But aside from them, all valid, the main point is that the use of jet bridges is charged an extra fee from the airport. Some airport charges for use, some charges for time, so a low cost company which is trying to save money is going to save on the jetbridge too.

So there are fees for the bridge over and above the stand next to it?

Yes, their are both "ramp" and "gate" fees. The ramp fee is much less than the gate fee.

Well, for example, I did a quick search and found the official fees for an Italian airport (Orio al Serio) and if I'm not mistake it has an additional fee only for the jet bridge. So bus transportation seems to be included in the basic fees, and if you want to use the jetbridge you pay on top of that.

@motoDrizzt that's because the bus is required if the airport chooses to put you on a remote stand, the jetbridge is an option if you don't want your passengers to have to use stairs.

It is not always about the extra fees.
Boarding and de-boarding via the jetbridge is a lot slower than using two stairs. You are using a single door instead of two, the people walk slower, there is a complex balance procedure to prevent the plane from tipping, etc, it just takes longer time. Many low-costs operators are sporting 30 or 25 mins turn-arrounds, so losing 5 or 10 extra minutes during boarding (and then having to pay extra for the priviledge) is not something budget airlines are keen on.

Radu094 is absolutely correct. the time for boarding/deboarding is cut in half.

Given the extra time for non-jetbridge passengers to walk to and from a plane, I'd like to see documents backing the claim that jetbridge embarkation/disembarkation is slower.

I have no ideea what document you think exists, but jetbridge is slower. Remember that for stairs the pax are usually pre-loaded into buses, so you are comparing same walking distances ( for jetbridge people still have to walk to the plane, unless you have some magical jetbridge)

@Radu094 not always, on many airports the distance between the exit of the terminal and the aircraft stand you're boarding is very short and people just walk across the ramp. Sometimes the route is marked with tape or paint, often it's just a guy waving people in the right direction.

well, I still stand by, that the difference is negligable as no airport will have a 10 minute walk-in through the apron to the airplane. Anyway, just to get technical :-p, the extra distance is just latency while the problem is throughoutput

I've had to board planes through stairs several times, and in my experience the call for boarding is always earlier than when a bridge is used. If you don't have some references I may have to assume this is just your guess.

hmm.. I seriously doubt there is any official reference/study on this, outside the airlines internal statistics, but I do 4 boardings/day every day in airports throughout europe. Stairs are twice as fast, and the preferred method because of speed. Jetbridges are not that much expensive, and my company would gladly pay 10 times the jetbridge fee if it meant faster boarding

Of course: I am only talking about the time interval from first pax aboard the aicraft until boarding is complete. Individual passenger experience might be different depending on the bus transport, the waiting line at the bottom of the stairs ,etc it might seem longer than jetbridge

As Radu094 has already mentioned, minimizing the gate turnaround time is usually the number one goal for budget airlines. It is thus crucial to use both doors to board/deplane passengers, as that can obviously almost halve the necessary time. In my experience (about 100 flights in Europe a year, maybe half of that with EasyJet), this is the norm and boarding only via the front door happens very rarely.
I have never seen a budget airline use one of the posh dual-jetbridge gates to board an A320, so that inevitably sends some passengers to the tarmac. On some airports, the design of the gates makes it possible to use both the jetbridge and the stairs at the same time (the front half of the aircraft boards via the jetbridge, the other half is sent to take the stairs). If this is not possible for some reason, then the jetbridge simply won't be used.
In fact, at some airports (for example PRG), there's usually a gate agent standing at the junction of the stairs and the jetbridge, checking everyone's boarding passes and sending them the right way. Other airports rely on information screens or instructions on the boarding pass like "rows 1-15 via the front door, rows 16-30 via the rear door", but that's much less efficient as there are always some folks taking the front stairs even though they're seated in row 28, which .

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Do flying boats carry anchors?
Inspired by the first comment here, and considering they are called "boats", do flying boats (or seaplanes) carry anchors?

A quick google search (I just searched for "flying boat anchor") finds https://en.wikipedia.org/wiki/Blohm_%26_Voss_BV_138 which shows an image titled "Blohm & Voss BV 138 at anchor on Lake Siutghiol, near Constanta, Romania in 1943." So, yes, at least some do, or at least did.

And if they carry anchors, are they different from normal heavy boat anchors? Weight is not so much as issue ona boat.

Unfortunately there is no english translation, but the swiss law regarding the swiss and german lake constance implies that all kinds of floating devices (except smaller rowing- and sail boats, but including seaplanes) have to carry anchors.

@Koyovis there are a multitude of anchor types; some of them rely more on mechanically getting purchase on the bottom than just using weight to remain in place.  This is equally true for say, small sailboats, where reducing weight makes the anchor both easier to store and use.

I can confirm they had one: I was lucky enough to own an HU-16 Albatross, many years ago. Prior to my purchase the bird was down in Arizona, near the Davis-Monthan boneyard.
It still had the original Grumman issues anchor mounted in forward compartment.  What I don't remember is what material it was fabricated from:  I think it was aluminum, and remember thinking of it being novel..  but it may have been bronze.
Either way, they definitely came originally equipped with one.
--
The Albatross, though underpowered, was an amazingly durable bird.  Some compelling stories float around about them rescuing downed pilots in Korea and Vietnam, landing in tiny creeks and ripping the floats off on banks.
Fun fact: An albatross that had struck a submerged log and had the bottom ripped out was sent to Australia for repair.. At the facility they didn't have the correct rivets (flush head, chamfered) and so they used normal button head rivets for the repair job... After this repair, it was discovered that this Albatross was able to get off the water at lower speeds than production birds..
It was so much improved that it was sent to Pax River for study.. It turns out that the use of button head rivets enabled it to break the water stiction at very low speeds.  The Navy (and Chairforce) then had custom rivets made and replaced all HU-16 lower hull rivets with them. They were custom because they had that chamfer.. So if you look at an Albatross rivet you will see that unique button-head with flush chamfer profile.

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Can you identify this twin engine propeller aircraft?

On the ramp at Orange County Airport New York.

My spidey senses are saying Saab 340 or 2000?

It is a Freight Runners Express Saab 2000.
Freight Runners Express is a US air carrier based in Milwaukee, Wisconsin, United States. The airline operates scheduled and on-demand air cargo and passenger services. Passenger air charter services are also operated under the Air Charter Express (ACE) brand using Embraer EMB-120 and Saab 2000 aircraft.1 Freight Runners is headquartered at Milwaukee Mitchell International Airport in Milwaukee.
Airliners.net Photo


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Why do propeller driven planes have intakes/inlets, such as this one on the P-51 Mustang?

Specifically talking about the p51, why do they have intakes? Don't propeller-driven planes not require any sort of intake because the propeller is what propels it by pushing air behind it?

@MichaelHall FWIW, my take was that the core point was that the OP simply didn't know what the intake is. The question about prop-driven aircraft needing inlets is still there, in the question body. As always, if an edit isn't helpful then you, the OP or anyone else is free to roll it back or edit again.

@MichaelHall Looks good to me!

@MichaelHall much better

Propellers are driven by engines, and engines burn fuel, and burning requires oxygen from the air. The intake supplies air to the engine. Burning creates heat, and air intakes also direct cooler air onto the engine to keep it from overheating.
In the case of the P-51, the duct you see is actually to feed the radiator. As the P-51's engine was water cooled, the radiator could be mounted in the belly of the airplane. The duct used the Meredith Effect to produce thrust through the expansion of air due to heating.

Isn't the big scoop on the p51 purely for the radiator though?

Yes it is @Sanchises, I was answering in general but I've edited to expand for this exact case.

The carb air intake is also clearly visible in the question photo, just behind and below the propeller spinner. It is smaller and less prominent than the radiator air intake on the belly.

The design of the P-51 means the engine radiator (a component of the cooling system) is situated behind and below the pilot, as in this diagram (from here):

Good answer to @pondlife’s edit, but this doesn’t address the air breathing nature of internal combustion engines that was implied in the OP’s unedited first version.

don't propeller-driven planes not require any sort of intake

No, propeller-driven planes (piston or turboprop) require air intakes for a variety of purposes:

Combustion air
Engine cooling (whether air-cooled or liquid cooled)
Oil cooling
Cabin ventilation and heating
Fuel tank venting

And perhaps more.

That’s the intake duct for the radiator for the liquid cooled engine. Similar to the radiator in your car, the radiator for the engine in the airplane is cooled by ram air from the intake passing through it and exiting a variable geometry ramp aft of it. Some of the air also bleeds off that ram air scoop and is fed through the oil cooler just below the radiator.
The smaller intake scoop just under the propeller spinner is the supercharger inlet that the engine aspires through.

I'd say Carlo Felicione is right, what is in lower part of fuselage, below wing, is an air intake for the radiator. P-51 cooling was arranged as to obtain thrust from heat, some speak about 50 kg thrust added.
The Cranfield repository includes many NACA, NASA and other aviation experimental studies. Paul Lamar, in rotaryeng.net published a booklet: 'Cooling your Wankel', describes extensively how the Mustang P-51 cooling works. Blessings +

The p51 has an inline engine which makes cooling with just air flow infeasible since the pistons are not all exposed to air flow equally. If you look at pictures of other WW2 era planes like the F4U Corsair or F6F Hellcat have radial engines where all the pistons are exposed to the airflow allowing air cooling. These pistons form circle at the front exposing them all to airflow. Because of the cooling problems the p51 was water cooled using an inlet scoop underneath the plane. Supermarine Spitfires also had inline engines and have a cooling intake underneath as well.

“Inline engine” means specifically that there's only a single bank of cylinders. Both the Merlin / V-1650 and the V-1710 are V engines with two banks. (Not that this changes much about the point regarding infeasibility of air cooling.)


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Planform Area of Commercial Passenger Airplanes
I am trying to retrieve information on the total area constantly covered by commercial passenger airplanes in flight (that is, airborne planes, not planes on the ground).
To this end, I've been trying to obtain formal/documented information (preferably from a source like the FAA) on the major types of commercial passenger planes, the total planar cross-sectional area (planform area) of each type of plane (as viewed from the top of the plane), and the average number of each plane type that is airborne at any time. I am looking for data similar to those shown here, which was in an article I've been reading. That data is from 2006, and I am looking for data which is recent (i.e. preferably within the last couple of years). Number of passengers and height of the aircraft is not important for me.
I've been searching on the FAA website, but I can't locate anything relevant. Don't know if it is just me, but I find it hard to easily search for information there. I welcome guidance on how to calculate said area based on freely-available data.

The FAA would have no reason to care about, calculate, or publish the average number of airplanes airborne worldwide so I don’t think you will find the information you seek there.

FWIW the correct term for the area covered by an aircraft as viewed from above is "plan section". ("Cross section" would be as viewed from the front or rear.)

@ymb1 Indeed, this is precisely the reason I am asking this question. I am trying to quantify the risk of the meteoroid and orbital debris environment on airborne aircraft (not aircraft on the ground).

Degree of Difficulty - I doubt much "space junk" comes in straight down. So you'd have to factor in reentry angle compared to whatever sq meter the aircraft body is consuming.


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Is it appropriate to determine approximate flight altitudes based on ADS-B landed altitude compared to runway elevation?
For small aircraft flying below 2,500 ft. AGL, is it appropriate to compare the landed ADS-B altitude (pressure calibrated AMSL) to the elevation of the runway in order to compute a reference offset for flight altitudes?
For example, if an aircraft's ADS-B reports a landed altitude of 700 ft. and the known runway elevation is 500 ft. above sea level, is it appropriate to apply that -200 ft. offset to reported flight altitudes?  Thus a reported ADS-B altitude of 1,500 ft. would be approximately 1,300 ft. for that aircraft/flight?
This question is regarding aircraft flying in the general vicinity of the airport and with relatively short flight durations (less than 20 minutes).
Edit: For clarity, this question is related to data from flight tracking websites such as FlightAware.

ASE answers, and other resources, linked in comments under this ASE question may be relevant: https://aviation.stackexchange.com/q/93379/34686

For an after-the-fact analysis, for example looking at flight data recorded by an EFB or displayed on a flight-tracking website, what you describe sounds very reasonable.
For use during a flight this is absolutely unacceptable; even for a flight conducted under Day VFR conditions, an aircraft must be equipped with a pressure-sensitive altimeter. In fact this pressure altimeter is what provides the transponder (ADS-B) with its altitude information in the first place (unless the parameter you are looking at is explicitly labeled "GPS altitude").
In an emergency situation where your altimeter becomes inoperative but the pitot-static system as a whole is still reliable, you might be able to justify the use of ADS-B altitude information to provide situational awareness until you land, which should be as soon as practicable—but the mental math required to correct the ADS-B altitude means it should be considered an emergency procedure only.

My guess is that OP wants to look at data from FlightAware (or similar) and try to apply a correction to the observed altitudes.

@Jim is correct that my question is related to sites like FlightAware (I've edited for clarity) but the additional information is helpful nonetheless.  Thank you.
So does this mean that the aircraft's altimeter should be calibrated for local pressure which would then make ADS-B out more accurate?

@bhamjman: See the question (and associated resources) linked by QF for more information. The upshot is: the altimeter in the aircraft is indeed calibrated as you say, but the altitude encoder which transmits information to ATC is never calibrated. Because the ATC radar scope knows the local altimeter setting, it automatically applies the correction on the ground. This ensures that ATC sees accurate information even if the pilot mis-calibrates their altimeter. It has the side effect that systems which do not calibrate the ADS-B information, like flight tracking sites, are inaccurate.

Thanks @randomhead.  So if I'm understanding correctly, the pressure altimeter can be calibrated for local pressure, and then the altitude value is fed to the ADS-B transponder for broadcast.  And I'm guessing this explains why multiple planes can all broadcast different altitudes (100-200 ft. variances) when landed?  QF's link has also been very helpful.

Not quite @bhamjman. The altimeter is a device which shows the pilot what altitude they are at, and the pilot can adjust this device to account for the local pressure. But the altitude sent to ATC, via the transponder, does not account for local pressure. It assumes that the local pressure is equal to the standard pressure and sends that information. The ATC systems on the ground then take that number and adjust for the actual pressure, just as the pilot adjusts the altimeter in the aircraft. It is possible that ATC and the pilot could use different adjustment factors.

Finally, what would you say is the reason for ADS-B altitude variances on the ground from multiple planes. In my example of a 500 ft. elevation runway, I'm trying to understand what contributes to ADS-B landed altitudes of 500ft, 600ft, and 700ft from 3 different planes.  Trying to understand why the ADS-B altitude data if off so much from one plane to the next.  I appreciate your time.

I would suspect it is variation in the physical equipment installed in the aircraft but I am not sure. Perhaps it is also a function of where the target "dropped off," provided the tracking site does not have coverage literally down to the ground. Both are merely guesses. That does sound like a question which deserves a post of its own!


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Understanding fuel tanks/pumps of Fighter jet
I have observed fighter jets performing maneuvers like inverting, Turing around in sharp angles etc. This may subject plane to G forces and other dynamic forces. How does fuel tank ensure steady delivery of fuel to engines in such dynamic conditions.

Related, possibly duplicate: https://aviation.stackexchange.com/questions/1183/do-fighter-jets-have-a-traditional-inverted-fuel-system

Thanks a lot @WPNSGuy

Most tactical fighter aircraft have negative and zero G time limits (on the order of approximately 10-30 seconds) reduce the risk of fuel starvation and ensure proper circulation of oil.  For this reason, and because it is far more comfortable on the human body, most maneuvers are done at positive G.
Most aircraft keep positive pressure in the tanks via bleed and ram air to to ensure proper feeding of the pumps.  Any system based on pressure and gravity at 1 G should function as well at higher positive G loads.  It's really zero or negative Gs that present problems.
Demonstration aircraft like the Blue Angels who may spend more time inverted at -1G are fitted with special swiveling pickups to ensure fuel and oil can keep moving where they need to go.

Under Positive G how does it ensure that pump always have access fuel, in previous comment it was mentioned about air pressuring the fuel. Can you elaborate little bit on that as well?

I added the middle paragraph, please let me know if that clears anything up.  Really any more detail would probably be aircraft specific.

Thanks a lot this explains really well


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How do I submit a NOTAM?
I (a hypothetical person) am involved in an activity like laser light shows, model rocket launches, fireworks displays, or construction which I think might be important to pilots. How can I submit this information to the FAA so that they can issue a NOTAM?

When I have had to file NOTAMs for skydiving demonstration jumps, I just called AFSS (1-877-4-US-NTMS) and asked to file.  The folks at Lockheed are way more helpful than the Feds used to be and will walk you through the process, but it is still good to have your information together before you call.  At a minimum you need a description of your activity, altitudes in MSL, times in zulu, and a location.  Location should be in reference to an aiport or nav aid ("Within one nautical mile of the BFE airport", or "27nm from the BADGER VOR on the 340 radial, for a radius of 2 nm").  If the activity requires authorization, you will also need to have that squared away before calling.

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Did SR-71s have a switch for seat height adjustment for the pilot or were there strict height requirements in order to fly it?
I've realized that nowadays there are switches present on most modern aircraft which electrically adjust the height of the seating position, and I was wondering if that mechanism was present on the SR-71? The reason why I wonder this is because the pilot's visibility was quite restricted in terms of forward visibility which would only make everything worse if the pilot happened to be shorter than other pilots in the unit.

The Air Force was the first to recognize the importance of making everything adjustable, to keep their pilots from having accidents.  https://www.thestar.com/news/insight/when-u-s-air-force-discovered-the-flaw-of-averages/article_e3231734-e5da-5bf5-9496-a34e52d60bd9.html

According to the POH the pilot could indeed move the seat up and down

(source)
Its worth noting that the SR-71 was a spy plane and visibility from the cockpit was not necessarily a critical aspect of the design. The aircrafts primary role was to cary photographic and sensor equipment, not to spot things from the front seat.

Very interesting. It does make sense that forward visibility was never a priority, I just think it would be harder for the pilot to see in front visually when approaching a runway for landing. Nevertheless, thank you. I was looking all over for this and couldn't find it.

@M66 the RSO could adjust their seat as well, if you look at the blurb it states the RSO had 6.75 inches of adjustment.


text:
Do F-22 Raptors have different chemical colored coatings on the canopy?
Today I saw an image of a couple of Raptors parked at Spangdahelm AFB and I noticed that one of the Raptors in the image had Golden-tinted canopy glass while the other one had orange-tinted Canopy Glass. I've also seen some images of F-22s at Elmendorf with the orange/reddish canopy glass tint similar to that of the F-35s canopy. I always thought the raptor had the gold tint, but this picture proves it wrong because it's pretty clear to see the difference in tint at the same angle. I'm also curious if it's ever been stated which chemical is used for the orange/pinkish tint since it's been said previously that the gold tint used on some raptors is Indium Tin Oxide.

What's the original source of your bottom photo? Looks like cgi to me; is it?

@RalphJ I really thought so too, but it's from real DoD footage: see here at timestamp 3:14. The still image is heavily postprocessed with dynamic contrast compared to the video.

I would think that the differences in the first picture could be explained by differences in cloud cover. You'd be shocked at what the slightest change in lighting will do to a photograph. Even the light bouncing off the side of 088 will effect the color of the reflection on 079's canopy.

@FreeMan since I didn't want to post the full picture because it would make the Raptors look harder to see, but there is a full image with 4 Raptors in the picture (2 just cropped out in this image) 1 raptor too had the orange tint and the other next to it had a gold tint. I don't think it would be clouds considering those two cropped out were further away from these with the same tints.

@FreeMan sidenote: I found a vid that shows the Raptors landing in germany with obvious differences in tint despite weather. https://youtu.be/AAf_dTVcoms

Even very slight differences in lighting can make a huge difference in the appearance of color. Go hang out at [photo.se] for a bit and look through some of the lighting questions. When you're outdoors under natural lighting, it changes moment by moment and no picture is perfectly evenly lit.

No, all canopies manufactured for the F-22A aircraft are done in an identical fashion. It’s just lighting reflecting off the canopy at different angles, different backgrounds behind them, etc.
It might also be possible that one represents a later production example  of the F-22, where the indium oxide coating process on the canopy was altered and improved for whatever reason (better durability, reduced RCS, etc.).
UPDATE: another possibility here is that this change in canopy color is a result to prolonged exposure to UV light during service. I make the suggestion, because I have observed the exact same effect on F-35 aircraft as well.

There is a video of the f-22s landing and taxiing with obvious differences in tint same weather and same timing (check my response to FreeMan). I'm aware all Raptors had the Indium tin Oxide tint from the start of manufacturing, but I'm still not convinced this orange tint appearence is in the case of lighting. I'd assume the raptor has received some sort of RCS related upgrades recently, and if you notice there aren't as many recently taken images of F-22s with golden canopies unlike back then.

Look carefully in a lot of these videos and photographs, you’ll notice that the aircraft with a darker tint to the canopy are also placed in front of a darker background. I suspect this has a dramatic effect on how the camera captures light from the canopies.

I saw two F-22's last week at Easterwood Airport (CLL) in College Station, Texas. They had done a flyover with two F-16's the previous Saturday at nearby Texas A&M University during the national anthem for the Aggies vs. Alabama game. I took this photo on Tuesday when the two F-16's and one of the F-22's left. I saw the closer F-22 on multiple days, it always had the orange tint, sort of rose colored also which the photo picked up more on. Imgur won't show the photo details but my phone says that the photo was taken at 11:35 am on October 10th.

Interesting.  But the aircraft in the photos are F-35s not F-22s

@carlofelicione - I knew that! Or at least I did last week when I saw them and wondered about the unusual canopy color. I must have been thrown by the question on the same topic. So it seems like both F-22 and F-35 have something similar going on, as the orange/pink description matches very close to what I saw on the F-35's.


text:
Where can I find accurate information about fuel efficiency of Airbus vs. Boeing planes?
I am trying to understand the competitive positions of Airbus and Boeing's large civil aircrafts. I would imagine fuel efficiency would be very important to airline given its large component in the total costs of operating. Where can I get information on the fuel efficiency of the large major planes e.g. A320 vs 737 etc?
Thank you

I think large major planes would be the 777/747/787 and the A340/A350/A380 - the 737 and the A320 are "small" (single isle) aircraft - although they are the most popular models.

Fuel consumption is a very important issue, and much besides the airplane or engine manufacturer influences the final result. Both Airbus and Boeing publish only marketing numbers, and require a non-disclosure agreement before they reveal any meaningful figures.
Approximately three quarters of the progress in fuel consumption in the last fifty years has been achieved with better engines, and the airframe and better operational procedures contributed only the remaining quarter. If there is any difference between contemporary Airbus and Boeing planes, it is very small, and any advantage is usually reversed with the next upgrade or new model from either company.
Here is a related question: Atlantic fuel burn estimations. It has links to tools for fuel burn calculations.
For a first approximation, use 55 to 65 g of fuel per Newton-hour or 15 to 18 g per kN of thrust per second with modern jet engines. Please do not use the static thrust at sea level, but the actual thrust at the right flight Mach number and altitude. If you lack this figure: A modern airliner needs thrust equivalent to between 1/18th (5.6%) and 1/12th (8.3%) of its weight. In cruise flight at Mach 0.82 the higher number of 8.3% should be used.
Things which have an influence on fuel consumption:

Flight speed. Usually flying a little slower helps, but normal operations are already quite close to the optimum. See here for a related question.
Flight altitude. Flying as high as thrust allows helps, but is not always possible. See here for a related question.
Operating mass. Lighter aircraft can fly higher and have less drag. Excessive reserve fuel rules cause fuel burn to go up.
Flight path. Usually the direct route is best, but sometimes gains can be made by avoiding a headwind en route.
Proper piloting. Flying with a small amount of sideslip already destroys any advantage winglets might have, and drag goes up quickly with sideslip. This is mostly an issue for propeller airplanes, though.
Maintenance status of the engines. Engines lose a few percent of efficiency over their operating life.
Maintenance status of the airframe. Dirty wings or badly fitting doors produce more drag, and condensed water in the belly adds some additional weight which increases fuel burn. Condensed moisture can accumulate in the fuselage, and airliners in Africa can well have a few tons of condensed water onboard.

This is why in real life the fuel burn varies, so any published figures out of context are hard to verify.

"[A]irliners in Africa can well have a few tons of condensed water onboard." Because of climate conditions or lower maintenance standards? (Or both?)

@DavidRicherby both I guess. More condensation with large differences in day and night temperatures and/or high humidity. Plus lax(er) maintenance procedures allowing it to accumulate longer before being drained.

Exactly! South East Asia has similar climate, but better maintained planes. What causes condensation is high humidity on the ground and low temperature at altitude, not difference between day and night.

Good answer, but I would add that the opposite scenario is also very common regarding route selection: intentionally taking an indirect route in order to stay in a strong tail wind. This is especially common for routes that can make use of a jet stream. For instance, while aircraft flying from North America to Asia will usually take the shortest (great circle) path, aircraft flying to North America from Asia will commonly be over a thousand miles away from that path in order to stay in the jet stream.

For this you will need the Fuel Capacity, Range and Pax capacity data .
You can get the Fuel Capacity, Range and Pax capacity data from the  homepages of Airbus A320 and Boeing 737
Airbus A320 :
http://www.airbus.com/aircraftfamilies/passengeraircraft/a320family/a320/specifications/
Boeing 737 :
http://www.boeing.com/boeing/commercial/737family/pf/pf_800tech.page
Once you get those figures divide the fuel capacity by range and then further divide that by the pax capacity .


text:
After a crash, for how long is the airport closed?
International airports are busy places. For example, London Heathrow saw an average of 1,290 "air transport movements" per day in 2014. It seems that a crash at the airport, such as BA Flight 38, would cause major disruption.
Yet, according to that same wikipedia page, flight operations were resumed within hours and basically back to normal within a couple of days.
Another more recent example is Turkish Airlines Flight 1878 crashing on landing at Istanbul. Again, the airport "was temporarily closed".
How are airports able to keep disruption to a minimum after (what seems to me to be) a fairly major incident, potentially involving a wrecked plane sitting on the runway? How do they move the wreckage and re-open the airport so quickly?

In the case of the first example, the aircraft came down short of the runway. Other than freaking the hell out of passengers on later flights, I cant see there was much actual disruption to the runway(s).

The wreckage of Flight 38 was on the runway threshold. Would that not be in the way? How quickly can it be moved? I guess "how do they move wrecked planes?" is a separate question...

to quote Wiki "The plane passed above traffic on the A30 and the airport's Southern Perimeter road and landed on the grass approximately 270 metres (890 ft) short of runway 27L" - that's a long way from the threshold. And even so, a simple displacement of the threshold (Heathrow's runways are quite long!) would serve to keep the runway usable even if something were on the threshold.

@Jamiec That was where it initially touched down. It was still traveling over 100 knots at that time. It came to rest on the runway threshold. A 61-foot-high obstacle sitting on the runway threshold is a pretty big problem. My guess would be that the simply used the other runway until they could clear the wreckage.

@reirab - yes I know that, but the point remains - either use a different runway or displace the threshold (if able)... there are ways to deal with temporary obstructions that dont require complete shutdown of the airport.

It completely depends on the accident and airport.
For example if I crash land on 10R at San Francisco, and it's a fairly quiet time of day (eg below the capacity of one runway), the airport could just use 10L and continue operations as normal. Similarly if there was no wind they could just switch to 1/19 L/R instead of 10/28 L/R. I'll discuss this toward the end of this answer.
Even if the crash didn't damage the runway, if the accident didn't damage the runway and the aircraft could be safely moved the airport would be back to normal as soon as the aircraft was moved and the runway had been checked. This could be within an hour.
On the other hand if at a single runway airport, with severe damage to the runway and a need to leave the aircraft in situ to be inspected, it could take several weeks.
In the cases you mentioned, BA 38 landed short of the runway. The airport was closed to arrivals for a few hours, however, and hundreds of flights were delayed, cancelled, or diverted. In the meantime, the runway in question (27L) was closed entirely for arrivals until 3 days later when the aircraft was recovered. However the runway re-opened on the day of the accident for departures only. As Heathrow typically operates with one runway for Departures and one for Arrivals, this had minimal impact on operations: ref
In Turkish flight 1878, the aircraft impacted Runway 5, then again on Runway 35L, but as far as I'm aware no significant damage was done. The other runways were inspected and used until the aircraft was moved. Ataturk is a busy airport, but not so busy that it can't cope with the loss of a single runway. Again a few hundred flights were delayed, cancelled, or diverted.
In neither incident was wreckage left on the actual runway, so once inspected they could be used as normal. There was some disruption in both cases - although no more than that caused by bad weather. If the aircraft had remained on the runway in either case, however, and had the accidents been at a single airport runway (eg London Stansted rather than Heathrow), the airport would likely have been closed for several days.
Another interesting case is Asiana Airlines flight 214 - an accident at San Francisco which closed the Airport for a few hours, and the runway for around a day. The other two runways (1/19 L/R which are perpendicular, as San Francisco has 4 runways arranged as 2 pairs) re-opened after around an hour and meant there was minimal impact, along with the parallel runway (10L/28R) which re-opened 24 hours later. The accident runway (10R/27L) re-opened around a week later.
One thing to note is that in most cases, an airport only needs runways in one direction - so for example at San Francisco there is a lot of resilience in the runways. As long as the accident doesn't cause damage too close to the "crossover" of the runways, San Francisco should almost always be able to operate at near full capacity shortly after an accident, even with a runway closed, due to always having a pair of runways available. Airports such as Heathrow with a single pair of runways are less resilient

BA38 hit the ground short of the runway but continued to slide until it was sitting on the threshold: map on Wikipedia.

Yeah this has been discussed on the other answer, I'll edit mine when I get a moment - the main principle stands, though, that the aircraft was below the glide slope and therefore the runway could be kept in operation as far as I'm aware

+1 for the first sentence. For more minor accidents (e.g. a plane taxis off of a taxiway,) they might not close the airport at all.

@JonStory I find it a bit dubious that a 61-foot-tall obstacle sitting on the threshold would really be "below the glideslope" to the extent that the runway can still safely be used. I don't remember having ever been that high when crossing the threshold either as a passenger or as a pilot, except in the cases that I was intentionally landing (very) long. Even if you're aiming at the 1,000 foot marker, a 3 degree glideslope would have you crossing the threshold at 52 feet. Also, jet blast on the crash scene from arriving and departing aircraft would probably be undesirable.

I'll be correcting this soon: The runway was re-opened for departures only, which makes sense, on the 18th. As Heathrow usually operates with one runway for departures and the other for arrivals, this didn't significantly impede operations: http://theaviationist.com/2008/01/20/ba038-b772-crash-landing-at-heathrow/

Your last line has something of a false premise - once the initial rescue is over (and presuming that there's no implication that airport operations caused the accident), there'd generally be no reason not to re-open using alternative runways. Flight 38 wasn't moved for several days - it just wasn't blocking all of the runways!
Passengers might not enjoy the site of a stricken jet, but it's not a particular issue that they see it.
In most jurisdictions, the rescue and investigation authorities 'own' the scene immediately after an accident and it's essentially up to them. They'll generally take a proportional view depending on the circumstances - there's little to be gained closing an entire airport because an aircraft suffered a mechanical failure with few injuries. It won't help the investigation, it's not going to destroy forensic evidence, it isn't putting anybody in further danger and will only serve to annoy the public and lose money for the operators.
On the other hand - if controllers at London Heathrow had someone caused an aircraft collision resulting in fatalities then I expect the airport would remain closed for a lengthy period of time as investigators work to forensically analyse the scene.
It's not quite comparable, but after the Shoreham jet crash the road remained completely closed for a week, and only fully reopened after several.

Flight 38 wasn't blocking any of the runways, it stopped over 200 metres short :)

@JonStory It landed short, it didn't stop short. It actually hit the threshold of the runway. I'd not continue with my approach if this was in front of me:
http://deicinginnovations.com/wp-content/uploads/2013/01/BA-38.jpg

A good point - it appears to have stopped with the nose just over the threshold. I'd assume that meant the runway couldn't be used but I can't find a source to confirm either way. The number of flights cancelled seems low though, considering it was Heathrow - I'd have expected far more disruption with a runway closed for 3 days

I don't think an accident suspected to be caused by controllers would close the airport for lengthy period of time. All the relevant evidence in such case would be on the tapes in the tower and in CVRs and FDRs, so once these are collected, the airport could be reopened (with controllers from different shift), except if blocked by wrecks.


text:
Why is the detcord on canopies wavy?
We know that the wavy lines on the canopy are detcord, to shatter the glass in case of ejection.
Why are they wavy?

Perhaps it shatters a larger area per cord?

Possibly to shatter the canopy into smaller fragments.  Straight dets might just detach a large proportion, possibly leading to unwanted severe secondary strikes on ejecting aircrew.


text:
How high can propeller airplanes fly?
Is there a maximum height a propeller airplane could fly?
Some lower bounds for maximum flying altitude:

12,000m (39,370ft): Antonow An-70, produced 1994
12,310m (40,387ft): Lockheed Martin C-130J Super Hercules, delivered in 2012
12,500m (41,010ft): Piaggio P.180 Avanti, production started in 1986
29,523m (96,860ft): NASA Helios HP01, record altitude reached in 2001

Just for comparison: Low earth orbit is about 160,000m.
Upper bounds: I don't know. I guess at some point there is not enough air to get lifted.
And nobody build an airplane with solar cells that flies to space.
I guess important factors for such an upper bound are:

Weight of the airplane,
Size, shape and speed of the propellers
Speed of the propellers

If we extrapolate from the Helios, no matter how thin the air gets, if you can make a subsonic airfoil light enough, it should be able to be propeller driven. There is a limiting issue, which is that the speed of sound decreases with altitude, so a subsonic aircraft might have to travel very slowly (in indicated airspeed, which is not necessarily slow speed over the ground).

You don't specify the type of propulsion, which makes a difference... but essentially if you had a big enough propellor, wings large enough to create lift and a non-air-dependant engine (eg not a conventional or jet engine) then you could go to the very edge of the atmosphere. As long as there is air to push, you can push it. That's the theoretical limit.

you don't need a propeller to get up into the flight levels. Gliders regularly fly in the flight levels, sometimes over 30,000ft

It is a matter of power source (and engine aspiration in case of air breathing engines), wing loading and aerodynamic efficiency. With current technology, the limit is around 100.000 ft (30 km), as proven by Pathfinder and especially Helios. I doubt that much more is possible with really useable aircraft.
Aerodynamics first: The altitude factor of $c_l \cdot Ma^2$ tells you how much lift can be produced at a given flight Mach number, and the wing loading then gives you the minimum density for sustained flight. 0.4 is a good value for subsonic $c_l \cdot Ma^2$, and 30 kg/m$^2$ is a feasible wing loading for flight at 30 km. See this answer for more detail.
If the power source needs ambient air (piston engine), the plane needs triple-stage compressors or turbochargers, which have been tested up to 20 km altitude and should be good for maybe 24 km. They are finicky devices; Boeing Condor rarely flew at its maximum power because the stages of the turbochargers would oscillate in an alternating sequence of surges. One stage would race ahead, causing the other to surge, which made the first surge and free up the other to race ahead, and so on.
Above approximately 24 km, solar-electric propulsion looks like the best option currently. In all cases you can only fly subsonic, so the minimum practical wing loading will limit the maximum altitude. Aircraft like Helios are very delicate already, so they can only be launched in calm weather and are at risk of being blown away by high altitude winds. Payload is minimal, and depending what the aircraft is supposed to do besides flying high will give you a limit on the maximum altitude between 24 and 30 km.
Going to orbit in a propeller driven device is completely illusory. There is not enough matter to push against at higher altitudes, and the theoretical propeller diameter would be measured in Kilometers (or miles, if you prefer that unit). The structural mass would be prohibitive. Also, propeller thrust is inversely proportional to flight speed, and there is no way to accelerate with a propeller to escape velocity. The thrust would be just a rounding error away from zero at 7.9 km/s.
This speed is required to escape earth's gravity by flying fast enough around it so that the centripetal force equals the aircraft's weight and is called orbital velocity. The higher the orbit becomes, the more energy is required to reach it. In order to gain enough energy, a propeller aircraft would accelerate in the atmosphere to a speed quite a bit higher than the desired orbital velocity and then convert that kinetic energy to potential energy to lift its trajectory above at least 100 km, the internationally recognized altitude where spaceflight starts. Note that this phase of the flight requires inverted flight if the acceleration takes some time. The maximum flight Mach number would need to be maybe 12 or even 15 so this maneuver is possible at all.
In short: Going to orbit with a propeller? Forget it!

@user2813274: You are right, I should be more explicit.

"The higher the orbit becomes, the faster the aircraft needs to go." – Other way around, isn't it? For circular orbits, the orbital velocity is slower the higher up you go.

@TannerSwett What I meant is that you need to start with a higher velocity in order to reach the higher orbit. I admit that was not expressed clearly. I hope my edit improved the answer.

@TannerSwett Sorry for replying to such an old post, but I wanted to say that Orbital Mechanics is bizarrely counter-intuitive. In order to reach a high, slow-speed orbit you need to accelerate to put energy into your orbit. Inversely, to move from a high-altitude low-speed orbit to a high-speed low-altitude one, you have to decelerate and remove energy from your orbit. Slowing down is speeding up and speeding up is slowing down. Crazy, right?

Is the question meant to exclude situations where meteorological "lift" such as mountain wave assists the aircraft in climbing to high altitude?

@quietflyer. Wouldn't that make the question meaningless? When it's about propeller aircraft, the prop should do the lifting.

If talking "crewed" (aka "manned") aircraft, using propellers:
The Grob Strato 2C was a German experimental high altitude research aircraft. Powered by two turbocharged piston engines (dual PUSHER propellers) and featuring an extremely long span wing of composite construction, one aircraft was built in the 1990s, but was abandoned despite setting a world altitude record for piston-engined aircraft on its last flight ("crewed" record, not over-all)
1995, August 4: 60,897 ft / 18,561 m
Note: Unpressurised cabin record is the Caproni Ca.161:
1938, October 22: 56,850 ft / 17,330 m
The theoretical "max altitude" a propeller would remain effective is "the stratopause (formerly misspeak, 48,000 to 55,000 m above sea level)" ...the level of the atmosphere which is the boundary between two layers: the stratosphere and the mesosphere. In the stratosphere, the temperature increases with altitude, and the stratopause is the region where a maximum in the temperature occurs.
IMHO: Past this region there is not enough particle density for practical propeller use. This, approx. 50,000m altitude, is "possible" but exceeds any existing technology, at least on designs I have seen (like the previously mentioned NASA Helios's 29,524m)

A P3 orion made 45,018 in 1971.

That's technically an answer, but way too short on detail - especially as you know it's not the record.

Thank you for your answer. Where can I find news and information about this flight?

@A.I.Breveleri Some info here: https://www.avgeekery.com/p-3-orion-turboprop-46000-feet-happened/


text:
Can airplanes transmit/relay flight data to ATC's periodically while in flight?
The flight data recorder is one important piece of information in the event of a crash. Can this information not be transmitted or relayed to the ATC's while the flight is air borne so that they don't have to wait to recover the data recorder after a crash ? I mean to say that periodically the data can be sent back to a ground controller when the signal strength is high and it can be logged. Please let me know if there are any limitations to the amount of data that an air borne flight can relay back to the controller.

Hi, welcome to the site! Before posting a question, please search the site first in order to see if it has already been asked.

No, there's no data relayed like this to ATC. All ATC really gets is the filed flight plan, and then the transponder data. ATC just cares about organizing all the traffic in the skies, and making sure it is safe, orderly, and expeditious.
Some airlines use a system similar to this to relay maintenance data to the airline from the aircraft, that's how AF447 was found to have something wrong, and how they generally found it's location quickly(I think within 48 hours debris was found from the a/c due to the location info through ACARS(Aircraft Communication and Reporting System)). This system, and it's capabilities are optional and variable depending on what the airline wants to spend. This is why there's so much controversy over the loss of MH370, since they didn't have the full reporting schedule, and a very basic version.

no, the "controversy" is mostly wild speculation by conspiracy theorists.

Q1 - Position, altitude, speed, heading

Can airplanes transmit/relay flight data to ATC's periodically while in flight?

Yes
1) ADS-B

Large expanses of Australia and Hudson Bay in Canada, currently without any radar coverage, are now visible on ATC screens after strategic placement of low-cost ADS-B receiving stations

From Boeing
2) Inmarsat

Inmarsat has confirmed it has proposed to ICAO a free global airline tracking service over the Inmarsat network, as part of the anticipated adoption of further aviation safety service measures by the world’s airlines following the loss of flight MH370.

From Inmarsat

Q2 - Engine temperature, flaps setting, control inputs, warnings etc

The flight data recorder is one important piece of information in the event of a crash. Can this information not be transmitted or relayed to the ATC's while the flight is air borne

No
That would be inappropriate, ATC have no interest in or use for such data. It would be better for the data to be transmitted to the aircraft operator under rules set by a regulatory authority.
Not yet
Live-streaming of flight data has been proposed by IATA and has been investigated by the NTSB amongst others.

The U.S. National Transportation Safety Board (NTSB) has said it was studying the possibility of live-streaming data, but Tyler said a broad consensus would be needed between airlines, major manufacturers and regulators.
"It's very important that if we're going to have regulation covering this area, that it's done on a globally consistent basis,'' said Tyler, who joined IATA in 2011 after five years as chief executive of Cathay Pacific Airways.

can they? in theory, if they have the equipment and there's receivers for it in place. Do they? No, not to ATC or any other "official" organisation. To their owners/operators and sometimes manufacturers is becoming more common though.


text:
Why do some charts not have the "TRACKs are MAG" notification, while others do?
Why do some charts not have the "TRACKs are MAG" notification, while others do? As seen in the examples I gave below, some charts have "BRGs and TRACKs are MAG" notifications, while others only have "BRGs are MAG" notifications. While "BRGs are MAG" is written on the VOR Y and VOR X charts published in the AIP Turkey, "BRGs are MAG" is written on the VOR Z chart. When I compared all the direction information given in the charts, I could not see any difference, but there is such a distinction, what is the reason? Is there something about their definition (Track and Bearing)?
Charts
VOR X :

VOR Y :

VOR Z :

Also, as can be seen from the same example, some charts write "in FEET" while others say "in FEET MSL". Is there any special reason for this difference too?

The changes you see on Turkey AIP charts are likely an anticipation of future reference changes, both in bearings and altimetry. To prevent confusion, the current references are explicitly mentioned.
Instruments of the past: Barometer and compass
As you know the current convention for aviation, except for ADS-B is to use magnetic direction and MSL barometric altitude. There is an exception only for polar areas, where the magnetic declination is not reliable enough, and where true directions are used.
However these two references create problems. They were very useful prior to GNSS generalized deployment, but are now two burdens.

Magnetic directions are the legal reference as of today, and must be used to interact with crews and ATCOs. However, modern navigation computers internally store and manipulate true directions, this is a simple mathematical model to make calculations for navigation.
The legal magnetic value, when needed to interact with the crew, is just derived from the stored true direction, based on a magnetic model for Earth. As I already explained in another answer, the conversion is not done homogeneously by all units, different values can coexist in the system, creating a risk.

Likewise the legal reference for altimetry is still the pressure-altitude determined by measuring the static pressure and converting it with the law in the ISA model.
It's well known this measure is not accurate at all, except in the vicinity of a weather station delivering the local pressure, hence the need to use two methods: QNE flight levels in cruise, and QNH altitudes close to the ground.
Modern navigation equipment use the geometric altitude above MSL, derived from the ellipsoidal height (HAE), which is what a GNSS receiver determines, and a model of the mean sea level above the ellipsoid (geoid).

Instrument of the future: GNSS, opportunity to switch to geometric altitude and true bearing
There are two projects to replace the old legal references by modern ones more suitable for computers, and more accurate:

ADS-B already broadcasts the geometric (GNSS) altitude, while transponders still transmit the barometric altitude. This could be extended to other uses.

There is a plan to switch to true directions in a few years (less than 5 years).

Confusion during the transition
There will be a transition period for the documentation to be updated. Today directions are magnetic and altitudes are barometric. There is no need to mention it on charts, as this is a requirement from ICAO (Annex 4 and Doc 8168). But at some point in time the assumptions will change. Without adding explicitly which references are used, it'll be impossible to decide whether a chart has been designed using the old or the new conventions. There will be a transition period where the conventions used have to be explicitly indicated.
Turkey authorities are likely adding the explicit annotation, in order to anticipate the need to know in the coming years: These charts have been designed with "magnetic bearings" and "altitudes MSL" (barometric).
"Tracks and bearings" vs. "bearings" only
There is a difference between a track and a bearing: A bearing is measured relatively to a fix or a facility, while a track is the direction of the path in general.

On the holding pattern depiction in your question, 206° is a bearing. This bearing also defines the track of the inbound leg.
On the other hand 26° is not a bearing, but a track.

It's more appropriate to talk about bearings (which also include radials) and tracks. Turkey likely updated their template in order to be more accurate, though this makes little difference here.
Altitude unit: Foot
Foot is a secondary unit for altitude. ICAO, deeply rooted in the Old World, has embraced its metric system since its creation, and stated since a long time the meter is the primary unit to be used for altitudes and distances.
Nobody used it when it was decided, a transition period principle was agreed, without specifying a deadline (typical of projects which are not going to complete). We are still in the transition period, and there is little craze for moving on.
So far a few States use this unit. The Russian Federation (as a legacy of USSR) and China do work with it as their standard. Russia, China and Turkey are all partly or totally Asian countries, close to each other.
It's possible the non-standard altitude unit (foot) is mentioned because of this proximity with large fully compliant countries .

That may be nothing more than a case of a change in the "boilerplate" language between the time that one was designed & published and when the others were designed and published.  Or even that a designer copied "this" text in one case and different text in the other.  I don't see anything there indicating that the difference in verbiage makes any actual difference in anything.
It's certainly not like they're publishing a track referenced to True North in one but Magnetic North in the other!

What you said might have made sense to me, but 3 of these 3 charts were amended with the same amendment document (AIRAC AMDT 02/21). In addition, the validity dates of these 3 charts are the same (22 APR 21). Considering that these documents, which were changed at the same time and whose validity date began at the same time, were prepared by the same people at the same time, the only thought that would justify what you said might be that the chart was prepared without paying attention to the details. @Ralph J

The amendment may have been something else, and the BRNG or TRK+BRNG notations may have been from longer ago (like when the procedures were created) and nobody bothered to harmonize those notations across the charts.  Bureaucratic process, if it doesn't need to be changed, leave it alone, even if it would seem to make sense to change it -- maybe somebody else had a reason for doing it this way. (Even though they often really didn't.)  I really wouldn't read too much into this.

@pilot162, to Ralph J’s point, an amendment does not mean that the procedure documentation is completely rewritten. If the amendment didn’t actually change that boilerplate language, it would not be changed.

I got the point, but it bothers me that the authorities that make up the chart are so careless. Even though it is boilerplate language, some things should be standard so that the chart reader is not confused when comparing.


text:
How can a surface created with asphalt be considered "Rigid" and not "Flexible"? Isn't concrete that is rigid and asphalt that is flexible?
How can a surface created with asphalt be considered "Rigid" and not "Flexible"? Isn't concrete that is rigid and asphalt that is flexible? This was also stated in the answer to another question. I also share the sample image for understanding. However, such a table is given on the Turkey AIP AIRCRAFT PARKING/DOCKING CHART (AD 2 LTAF PRKG-1). Shouldn't the letter in the first digit of the series given for the apron D, which is asphalt here, be "F" instead of "R"?

---> This text was taken from the answer to the question at this link: https://aviation.stackexchange.com/a/33444/65367

I would change that definition as "Asphalt is usually a flexible surface, Concrete is usually a rigid surface".
I do not have specific knowledge of that airport, but it may be that the surface is a composite asphalt+concrete:

In such case, the upper layer is asphalt, and this is why the indication in the chart is probably Asphalt (this is a my guess).
A composite material may be rigid or flexible depending on the ratio between asphalt and concrete used:

The choice of the pavement type, i.e. rigid (R) of flexible (F),
should be based on the chart used for the evaluation.

Source: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/552405/DMG_27.pdf

It is possible that either the surface type or PCN classification for this particular apron is either incorrect or out of date. While this is not the usual thing that you would first suspect when viewing an official aviation document, I think it might be plausible in this case if we put this particular piece of pavement into perspective.
The apron being discussed is at Adana Sakirpasa Airport (ADA, LTAF) in the city of Adana in southern Turkey. Opened in 1937, Adana Airport is Turkey's oldest commercial airport and its sixth largest. The airport is located in the middle of developed areas of the city, and is expected to operate only until the completion of the Cukurova Regional Airport located 20 km outside of the city, which is currently scheduled to open sometime in 2023, although the project seems to have been delayed.
The two pavements being compared, Apron A and Apron D, can be seen in Google Maps satellite view.

Adana Airport (source: Google Maps, imagery: CNES/Airbus, Landsat / Copernicus, Maxar Technologies)
Apron A is located at the passenger terminals, and looking at some random online photos it appears to see mostly 737 and A320 sized airliners. Although the terminal gates can handle aircraft up to A300 (and even 747!), as seen in the DHMI (Turkish Airport Authority) document which also contains the PCN information shown in the question.

LTAF Parking Diagram (source: www.dhmi.gov.tr)
The comparatively tiny Apron D, which is in question because of its confusing surface type designation in the DHMI documents, appears to be sized to hold a small number of general aviation aircraft. Looking at a close-up satellite view it appears that the east section of Apron D can handle up to eight small aircraft, similar in size to the five aircraft seen parked there in the satellite photo, which seems to include a small twin-engine plane.

Apron D (source: Google Maps, imagery: CNES/Airbus, Landsat / Copernicus, Maxar Technologies)
Meanwhile it appears that a hangar has been built on the west section of Apron D. Although it can be noted that the DHMI document still shows eight parking spots in that section, the markings for four of them can still be seen in the photo.
The lack of any apparent facilities at Apron D would seem to indicate that this apron is mainly used for longer term small aircraft storage. A larger general aviation apron with facilities, Apron C, is located on the north side of the airport next to Apron D which is a military apron.
Another DHMI document for Adana Airport lists surface information for all of the taxiways and aprons.

LTAF Apron, Taxiway Information (source: www.dhmi.gov.tr)
This document appears to be current as of January 2023.
It can be noted that all of the taxiways are listed as asphalt except for A1 and E, which go to aprons B and C respectively. Apron D is the only apron listed as asphalt on the document. It can also be noted that Apron D has the exact same PCN values as Apron A, with the only difference being that the surface for Apron D is listed as asphalt. This could be an indication that either the surface type or PCN values listed for Apron D is incorrect or out of date.
It can also be noted that while Wikipedia lists the Adana Airport runway as asphalt, the DAFIF (Digital Aeronautical Flight Information File) information that Wikipedia references was current only as of 2006, which is when DAFIF stopped being available publicly. An unofficial source which appears to be current as of 2016 shows the Adana runway as being composite, a surface type mentioned in another answer.
Looking at all of this in context, it seems possible that since Apron D seems to be used by only a small number of small plane owners, that any errors or inconsistencies as far as surface type classification in the DHMI documents have likely gone unnoticed, or ignored. Especially considering that the Adana airport is expected to close in the relatively near future.

First of all, thank you very much for your detailed answer. However, while the shared documents are created and made available by authorized professionals, I do not understand the idea of not correcting the errors and republishing them in the same way. It shouldn't be too difficult to correct something that is known and publish it. As you know, aviation is a serious business and everything must be carried out meticulously. Even if your answer is correct, my inner self cannot accept this ignoring. Thanks again for the answer..

In general I agree, most things on aviation charts can have important implications. Considering how heavy many airplanes are, surface strength is important for the safety of the aircraft using the surfaces. But primarily it's important for the service life of the pavements. Airplanes too heavy for a particular surface will cause it to wear prematurely and/or require more frequent repairs. In this case however this is a tiny apron used to park a few small lightweight planes for storage. There is little chance that anyone even looks at the PCN numbers on the documents for this particular apron.

I have to look at these charts because I fly the small planes in the image you get from Google Maps :) Anyway, as you said, the authorities who prepared the chart may not pay much attention to it.

Not sure if you interpreted my comment to mean that no one looks at the charts. I was only referring to the surface classification for Apron D. If you were flying into LTAF in a small plane you would likely not be looking at surface classifications on the charts other than maybe to see if they are paved or not. PCN is important for larger planes, but it's doubtful that anyone flying into LTAF will be directed to park in Apron D, the people who park there probably have leases. I doubt any of them care if it was not classified correctly on the chart, or worry whether the PCN numbers are correct.


text:
What does the "EMERG BATT switch" and the associated phrase "(if starting battery installed)" mean?
What does the "EMERG BATT switch" and the associated phrase "(if starting battery installed)" mean? I could not understand what the "EMERG BATT switch" and its associated expressions (if starting battery installed) in the "INFLIGHT ENGINE RESTART" procedure in the emergency section of the Tecnam P2006T aircraft mean. Because even though I scanned the entire AFM of the aircraft, there is no information about the "EMERG BATT switch", which is referred to as the backup battery. Also, I didn't understand what was meant by the expression (if starting battery installed). I think I need a detailed answer. I am attaching to the question the image of the page where the procedure is and where these statements are mentioned.

This is not an answer, but from what I read online, the FAA required a second battery to be installed, specifically for in-flight restart. So this instruction seems to say... if you have the second battery installed, in case of first in-flight restart unsuccessful, retry with the second battery connected. It's likely a problem of insufficient current, and the two batteries are connected in parallel to prevent the voltage to drop when the starter is activated in the second attempt. The answer is likely in the FAA document, but I was no able to get it.

I understand and agree with everything you say. However, there is an article in the AFM document that I edited above. Do you think this means "Starting Battery = Emergency Battery"?

I think yes. I found a reference for the modification: MOD2006/049 “Engine Starting Battery”, but not the details. This mod is referenced in the FAA type certificate. And by the way the text you ask for is also applicable to single and dual generator failure procedures.

I think you have discovered one of my personal peeves:  When manufacturers and technical writers use different words to describe the same thing...

I get confused when the same thing is named differently and it drives me crazy too :)

While I have not worked on this type of aircraft, I believe that it has 2 separate batteries. One battery is used just for the starters. The second battery supplies power to the various aircraft systems such as lighting and avionics.
During normal operations the generators charge both batteries, but only the first battery is used for the starters and only the second batteries the rest of the systems. Placing the battery switch to emergency allows both batteries to power the starters. That way if something has happened to first battery, the second battery might still be able to restart the engines.

The point that I do not understand here is which battery we call emergency battery is? Engine Starting Battery or Main Battery? If we think that it is the Engine Starting Battery that feeds the starters to start the engine, is our emergency battery here the main battery?

I also added the backup (emergency) battery switch to the question. And am I supposed to understand that the function of this button is to connect the main battery to the engine starters since the engine starter battery cannot start the engine?

Motorhomes have a similar system.  It allows a second battery to be available for a re-start of the engine.

@pilot162, I think the reverse is true:  That the main battery starts the engines normally, unless you flip the switch to connect the Starter/Back-up/Emergency battery.  I say this because of the procedure that says "if starting battery installed..."  This makes it sound like an option, that perhaps not all aircraft have one installed.

I completely agree with what you said. It makes much more sense for the Engine Starting Battery to be a backup system. However, since I am not familiar with this system of the aircraft and I do not have enough data, I cannot be sure. But the argument you give is the most logical approach.

"One battery is used just for the starters", I think this is incorrect. The two batteries should be in parallel, but the second is normally switched off. This second battery is switched on in case of electric generator failure and/or for the second attempt of an engine inflight restart (this case also implies a lack of generator).


text:
Why cruise at 7000' in an A319?
I was on a flight from Philadelphia (KPHL) to Boston (KBOS), after some delay and some change of route due to weather, the captain announced that we will be cruising at 7000' due to delays in the area.
The history of the flight is here: https://flightaware.com/live/flight/AAL2606/history/20190618/2235Z/KPHL/KBOS
My question is two fold:

Why cruise so low with such an aircraft (A319)?
What is the impact on fuel consumption, knowing that we were also slower?

At that altitude, it is a violation of 14 CFR 19.117 to exceed 250 KIAS.  I doubt this flight actually flew at 7,000.   Flight Aware says it was filed for 17,000ft, and I suspect it actually flew at that height, but due to some technical error, the 10,000 part may have been left off?

Even 17000 is pretty low. The fuel burn would have been brutal.

Looking through the history, the flight is typically filed for about 23,000

@abelenky FR24 also showed it at 7000' so I think they really flew that low (and reported at ~290kts ground speed so probably 250KIAS). Although it's very curious indeed.

Yes, they crossed about 1100 reporting stations that identified them at the same altitude (about 7075), and the climb and descent rates match up with what is reported. It does look like that flight may have actually flown that low and very likely at 250 kts indicated. Since that altitude does come from the aircraft transponder, it could have been a faulty indication, but climb rates support the altitude. Now, if the flight attendants served drinks, then the flight was most likely over 10,000 ft.

I check with my phone gps it was 7000ft approx and the view to the ground was consistent with a flight that low. They also served drinks.

Not an answer as this is pure speculation, but there may have been an issue with the cabin pressurisation system, but it was easier for them to fix that in BOS than in PHL for whatever reason. 7000 ft is approximately the altitude the cabin is usually pressurised to, so that would be consistent.

Interestingly enough, the same flight on the next day (different plane) also flew at that low altitude. And the same plane on previous/subsequent flights did not have that issue, so it's definitely not plane-specific.

The captain said he was flying at 7000', flight aware says 7100', why is anyone doubting the accuracy of that?

Could it be possible that they flew this VFR to safe time? I can imagine with the weather around that ATC didn't had an IFR release for them until several hours. If I had the option of waiting two hours and then fly IFR through the weather or navigate around the storms VFR and land with less delay, I'd chose the visual route.

It was because they could get there faster on a "TEC route."
IFR flights are subject to congestion management at the ARTCC level, which means they have to wait their turn in line to be allowed into the airspace. That used to be done with holds (and still is in many other countries), but the US will slow down aircraft, reroute them or even delay takeoff to avoid holds, which saves fuel and therefore money. Most likely in this case, they were facing a long wait on the ground due to congestion in ZNY and/or ZBW.
However, if a flight stays low enough, it may be in contact with various TRACON facilities the entire way and never talk to an ARTCC, which means it can avoid the congestion and therefore leave immediately. This typically requires flying below 10k MSL for the entire trip, which is the normal boundary between the two. (It varies between 9k and 12k.) In fact, doing this in the NE US is so common that they've developed an entire suite of preferred Terminal En-route Control (TEC) routes to make it easier for both pilots and controllers.
Using TEC routes burns more fuel because the planes are flying lower and slower than normal, which is inefficient for turbine aircraft, but in some cases the airlines may decide that's better (i.e. less bad) than delaying or canceling a flight.

I'm not sure that the TEC part of your answer is correct, but the rest of the answer is. Departure delays for high altitude routes does occasionally leave the low altitude routes as the only reasonable option. I have never experienced this out of PHL, but I have often seen this out of TEB. TEB does not call it TEC routing, but low altitude routing.

@ymb1 Yes, a TEC (Tower Enroute Control) route is a type of route, but is not applicable here. A TEC route is by definition a published route (e.g., as found in the chart supplement). No TEC routes are published for PHL to BOS. The route flown shares many similarities with a TEC in that it was flown at low altitude and required no ATC service at the Center level. However, these non-published routes are generally called "low level" routes. Their use is relatively common, but they are not published.

The only reason for your flight to operate at such low altitude is because it is cheaper for them to do so.

As you said it is due to weather, other route/altitude may not be available. They can cancel the flight but that is likely to be costly. They may have to find accomodation for you and crew until they can put you to the next flight. Sub-optimal flight maybe better than no flight in this case.
They may need that aircraft at that location the next day. If they choose to cancel your flight today, they will have to find a way to have this aircraft or another aircraft to fill in for the required flight the next day. They might as well fly a slightly more expensive flight at lower altitude rather than fly an empty plane to Boston.
It is possible for them to wait for weather to improve but there is an issue of crew working hour. A pilot cannot work more than 8 hours in a day without provision for additional crew. They may approach that limit and the wait for weather to improve might means the airline has to provide another crew for the flight and might mess up crew schedule for the next few days.

So for the airline, in this case, flying lower and slower maybe a better option for them. Hence higher fuel comsumption is better than no flight.

That’s a typical alternate route to KBOS by sending them direct to FJC VORTAC thence routed eastward.  I suspect the real reasons for this are reduction of traffic congestion for NYC arrivals by ATC.  On lighter days, they’re typically given the ROBUC3 arrival into KBOS immediately after departure from KPHL.

Does that route necessarily imply such a low altitude though?

Not necessarily, but it can happen.  And obviously the crew felt it was acceptable and flew it as opposed to requesting a higher altitude.

@CarloFelicione Or perhaps they requested higher and were denied due to congestion that resulted from the storms.

Well they were filed for 17,000 ft.

If they had an issue with the pressurization system, they'd fly that low. Why not cancel the flight? Well, that'd cost money. It'd be cheaper for them to fly low, eat the extra fuel costs and make buck on passenger fare. Who knows, maybe the part needed was nearby so they were going to have to route the plane there anyways.

American's hub is in PHL. They wouldn't fly to an out-station to get parts. It also seems rather unlikely to me that they would operate a flight with a PACK and/or outflow valve inop. Does the MEL even allow that? Continuing flight under 10,000 if something goes inop while airborne is one thing, but knowingly beginning a flight with inop equipment is quite another.

Possibly, the flight was too dangerous at a high altitude due to complications in weather, and therefore they decided to fly lower and slower. Flying at 7000' is very fuel-consuming, but they could do it since Philadelphia and Boston are fairly close together.

You generally avoid adverse weather by flying ABOVE it, not below

@J.Hougaard True, but you have to take off and land. Staying below weather may be a more predictable scenario than climbing and descending through it, when you are only flying a 360NM route.

@alephzero The problem with weather is that is usually goes from ground level up to some upper level. There is very rarely a clear area below adverse weather (gravity tends to do its thing)